The present invention relates to a method and apparatus for a coil. More particularly, but not exclusively, the present invention relates to an eddy current coil for use in an eddy current sensing probe.
Eddy current sensing has long been used within the field of nondestructive evaluation (NDE). Although configurations can vary, in a typical application a probe with an eddy current sensing coil is placed near an object to be tested. A coil is activated resulting in the formation of eddy currents associated with the object under test. Analysis of the resulting eddy currents can be used to detect various parameters associated with the object under test. For example, in the context of aircraft a number of flaw types and sizes can be identified, including but not limited to stress fractures in an aircraft wing, corrosion in the vicinity of a lap joint, and other conditions. One skilled in the art will recognize that eddy current sensing is used in a variety of contexts or environments, especially critical components such as air frames, engine parts, nuclear power plant tubes, etc.
Conventionally, the coils for use in an eddy current sensing probe are formed by hand. The coil is formed by turning a wire a number of times around a core. There are numerous problems associated with this handcrafting method of forming of a coil. Many of these problems stem from the imprecision of this process. Slight differences in the number of turns of the coil, the spacing between the turns of the coil, the alignment of the coil on a core, and other difficult to control variations result in variability in the resulting coils and the resulting probes. Many eddy current coils have multiple layers of turns and more than one set of windings. Very thin wire (50 AWG) is sometimes used, making manufacturing an extremely delicate operation.
This variability is seen as a significant problem in the industry. In fact, at least one study indicates that current manufacturing techniques lead to a variability in performance as high as 400%. Variability can result in difficulties in calibration, increased time to perform an analysis or evaluation, and the potential for improper analysis if the variability is not taken into consideration during the evaluation process. Therefore variability increases costs in the performance of nondestructive testing using eddy currents.
Some of the common problems encountered with eddy current probes include difficulties arising from tilt of the windings, tilt of the ferrite core, or both. Another problem is chipped or otherwise damaged ferrite cores. These factors can all effect performance and will lead to variabilities that may be hard to account for. Model-based measurement techniques, often consider to be the future of quantitative eddy-current nondestructive evaluation, may be inaccurate as a result of such variabilities.
It is further noted that wire twisted or turned within a probe body can lead to stray inductance and can also adversely affect the electrical properties of the probe. What is needed is a method to reduce variabilities due to probe internal connections.
Another problem with eddy current sensing is the amount of time required to inspect a component or surface. It would be advantageous to reduce the amount of time involved in inspecting such a component or surface.
Therefore, it is a primary object, feature, or advantage of the present invention to improve upon the state of the art by providing a method and apparatus for a coil for use in an eddy current sensing probe.
It is a further object, feature, or advantage of the present invention to provide a coil for an eddy current sensing probe that is conducive to being manufactured through automated processes.
It is a still further object, feature, or advantage of the present invention to provide a coil for use in an eddy current sensing probe that reduces manufacturing time and costs.
Another object, feature, or advantage of the present invention is a method and apparatus for a coil for an eddy current sensing probe that is not limited in size or performance by handcrafting techniques.
Yet another object, feature, or advantage of the present invention is a method and apparatus for a coil for an eddy current sensing probe that includes multiple stacked windings.
A still further object, feature, or advantage of the present invention is a method and apparatus for a coil for an eddy current sensing probe that improves accuracy by reducing the differences between models of the probe and the actual probe.
Another object, feature, or advantage of the present invention is to provide an array of coils for use in eddy current sensing.
Yet another object, feature, or advantage of the present invention is to provide an eddy current sensor configuration that allows for quickly scanning a component or surface.
A further object, feature, or advantage of the present invention is to provide a coil for use in an eddy current sensing probe that is easy to construct.
A still further object, feature, or advantage of the present invention is to provide a coil for use in eddy current sensing that allows for convenient inspection of complex parts.
Another object, feature, or advantage of the present invention is to provide a coil for use in eddy current sensing that allows for positional reproducibility in the inspection process.
Yet another object, feature, or advantage of the present invention is to provide a coil with a molded body to improve positional reproducibility associated with an inspection process.
One or more of these and/or other objects, features, or advantages of the present invention will become apparent from the specification and claims that follow.